I've done injury rehab on the turbo riding like this. Should be good for the thumb bleeding as its up. I managed 2-3 hours at a time of Z2 like this and 30 min Z3 blocks were fine
It was more to do with the intensity I could maintain whilst still being comfortable rather than boredom although it is boring. I just found I grip the bars alot harder for more intense efforts. Nowhere near as bad as yours but I couldn't grip the bars for 3 weeks after this one
I've done injury rehab on the turbo riding like this. Should be good for the thumb bleeding as its up. I managed 2-3 hours at a time of Z2 like this and 30 min Z3 blocks were fine